Western Civilization has been slipping for far longer than cultural Marxism has been around. The attraction of CM is a symptom, not the disease. George Santayana noted in around 1900 that the only purpose American Civilization seemed to have was to increase the gross national product and the life expectancy.

The problem started when nothing could be found to replace the social function of religion. The tremendous prestige of science has blinded most people to it's limitations in a materialist view of the universe. A few people are able to live fulfilling lives as more or less balanced, rational beings but most fall into romanticism (worshiping your own emotions) sensualism or existential despair. Cultural Marxism is a cult of sensual, materialist, existential despair. It seeks to perfect humankind by making them inhuman.